Antifreeze admixture for concrete

Abstract

A method and composition for making concrete includes an antifreeze admixture which is added to the concrete to prevent the freezing of water in the concrete when the concrete is cured during the winter or other cold conditions. The concrete admixture includes sodium nitrate and sodium sulfate combined with one another in a predetermined ratio. In a preferred a embodiment the ratio of sodium nitrate to sodium sulfate equals 3:1. A dosage of greater than 2% by weight of cement of the above described admixture was found to significantly increase the compressive strength of concrete cast of cold (below freezing, or 0 degrees celsius) temperatures, and dosages of 6% and 8% by weight of cement of the specified admixture were found to be particularly effective.

What is claimed is: 
     
       1. An admixture for concrete consisting of: a) sodium nitrate; and   b) sodium sulfate, wherein said sodium nitrate and said sodium sulfate are combined with one another in a ratio of sodium nitrate to sodium sulfate of 3:1.   
     
     
       2. A concrete mixture consisting of: a) concrete;   b) water; and   c) an antifreeze admixture consisting of sodium nitrate and sodium sulfate in a ratio of sodium nitrate to sodium sulfate of 3:1 and wherein the admixture is present in the amount of from 2% to 8%, by weight of the mixture.   
     
     
       3. A method of casting concrete comprising the steps of: a) preparing a concrete mixture consisting of concrete, water, and an antifreeze admixture consisting of sodium nitrate and sodium sulfate in a ratio of sodium nitrate to sodium sulfate of 3:1, wherein said antifreeze admixture is present in the amount of from 2% to 8%; and   b) hardening said concrete mixture into a form.   
     
     
       4. The method of claim 3 wherein the steps take place without freezing of said concrete mixture.